It looks like that group has died. Google says this:
==Banned Content Warning
The group you are attempting to view (alt.machines.cnc) has been
identified as containing spam, malware, or other malicious content.
Content in this group is now limited to view-only mode for those with
access.
Group owners can request an appeal after they have taken steps to
clean up potentially offensive content in the forum. For more
information about content policies on Google Groups see our Help Center
article on abuse and our Terms of Service.
==
I didn't see any new content, just really old stuff from archives...

Agree that there's very little activity on a.c.m. I use a lot of
keyword filters, and those may have nuked some legitimate posts, but the
the group looked all but dead. One message on 1/14/81, then 2-3 bqck in
Sept '17, and so on.
(Technically, A.M.C is a USENET news group - just like R.C.M. is a
USENET group. Google doesn't own it or control any aspect - it only
controls what access/content it's own users can see when using it's
services. )
Email address is a Spam trap.

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